Heat exchanger, liquefaction system with dual refrigeration cycle comprising said heat exchanger

ABSTRACT

A heat exchanger having a plurality of heat exchange bodies, each heat exchange body having a first inlet configured to receive a first fluid, a first outlet configured to discharge a second fluid, a first distribution means for the first fluid, which is connected to the first inlets of the heat exchange bodies, the first distribution means having at least one main distribution duct, a first discharging means for the second fluid, which is connected to the first outlets of the heat exchange bodies, the first discharging means comprising at least one main discharging duct. The plurality of heat exchange bodies may have a first set of heat exchange bodies mounted in parallel and a second set of heat exchange bodies mounted in parallel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119 (a) and (b) to French Patent Application No. 1910526, filed Sep. 24,2019, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The technical field of the invention is that of the liquefaction of a gas mixture. The present invention relates more particularly to a heat exchanger particularly designed for the liquefaction of a gas mixture. Furthermore, the invention relates to a liquefaction system with a dual refrigeration cycle comprising such a heat exchanger.

BACKGROUND OF THE INVENTION

It is known practice to liquefy natural gas in order to be able to store it and transport it over long distances. Natural gas is a gas mixture mainly made up of methane but also butane, propane, ethylene, ethane, or nitrogen. Among the techniques used for liquefying natural gas, the liquefaction process with a dual refrigeration cycle, also known as DMR for “Dual Mixed Refrigerant”, is particularly advantageous in terms of energy efficiency. In particular, the DMR process consists in carrying out a first refrigeration cycle at a temperature of around −60° C. in order to condense the heavier compounds and then a second refrigeration cycle at a temperature of between −60° C. and −170° C. in order to liquefy the lighter compounds.

FIG. 1 is a schematic diagram of a liquefaction system 1 with a dual refrigeration cycle for implementing the DMR process. With reference to FIG. 1, the liquefaction system 1 comprises a distribution duct 2 through which the natural gas to be liquefied is introduced, a pre-cooling heat exchanger 3 that carries out the first refrigeration cycle, a liquefaction heat exchanger 4 that carries out the second refrigeration cycle, and a discharging duct 5 via which the liquefied gas is discharged.

Each heat exchanger, i.e. the pre-cooling heat exchanger and the liquefaction heat exchanger, comprises a plurality of heat exchange bodies mounted in parallel, one after another, which transfer heat between the cooling fluid and the fluid to be refrigerated, through a heat exchange surface. However, the heat exchange bodies exhibit differences that are due in particular to the manufacturing tolerances of the heat exchange bodies and/or to the distribution between the heat exchange bodies in the heat exchanger. These differences bring about heterogeneity in the flow rates, the temperatures and the pressures of the fluids circulating in the heat exchange bodies, The state, i.e. gas/liquid, of the fluid exiting the heat exchange bodies then varies from one heat exchange body to another, and this can cause the liquefaction of the natural gas to be unstable and/or partial.

SUMMARY

The invention provides a solution to the abovementioned problems, making it possible to optimize the distribution of the fluids between the heat exchange bodies of a heat exchanger.

A first aspect of the invention relates to a heat exchanger comprising:

-   -   a plurality of heat exchange bodies, each heat exchange body         comprising:         -   a first inlet configured to receive a first fluid,         -   a first outlet configured to discharge a second fluid,     -   first distribution means for the first fluid, which are         connected to the first inlets of the heat exchange bodies, the         first distribution means comprising at least one main         distribution duct,     -   first discharging means for the second fluid, which are         connected to the first outlets of the heat exchange bodies, the         first discharging means comprising at least one main discharging         duct,         the plurality of heat exchange bodies comprising a first set of         heat exchange bodies mounted in parallel and a second set of         heat exchange bodies mounted in parallel, the first set of heat         exchange bodies and the second set of heat exchange bodies being         disposed symmetrically with respect to said at least one main         distribution duct of the first distribution means or with         respect to said at least one main discharging duct of the first         discharging means.

A “heat exchange body” is understood to be a device for transferring heat from one heat transfer fluid to another without mixing them.

Thus, unlike the heat exchangers of the prior art, in which the heat exchange bodies are mounted in parallel one after another, the heat exchange bodies of the heat exchanger of the invention are arranged symmetrically with respect to a central axis, i.e. the axis of the main distribution duct or the axis of the main discharging duct.

Such a symmetric arrangement of the heat exchange bodies makes it possible to balance the distribution of the fluids between two heat exchange bodies of the heat exchanger that are situated at an identical distance from the main distribution duct or from the main discharging duct. Moreover, the pressure drops that result from the conveying of the fluid along the main distribution duct and the main discharging duct are reduced. Therefore, the flow rates, the temperatures and the pressures of the fluids passing through the different heat exchange bodies are more homogeneous. Thus, the state of the fluids exiting the heat exchange bodies is likewise more homogeneous.

Aside from the features that have just been set out in the previous paragraph, the heat exchanger according to the first aspect of the invention may have one or more additional features from among the following, considered individually or in any technically possible combinations.

According to one non-limiting embodiment,

-   -   the first distribution means comprise a main distribution duct         connected to the first inlets of the first set and to the first         inlets of the second set of heat exchange bodies,     -   the first discharging means comprise:         -   a first main discharging duct connected to the first outlets             of the first set of heat exchange bodies,         -   a second main discharging duct connected to the first             outlets of the second set of heat exchange bodies,     -   the first set of heat exchange bodies and the second set of heat         exchange bodies being arranged symmetrically with respect to the         main distribution duct.

According to one non-limiting embodiment,

-   -   the distribution means comprise:         -   a first main distribution duct connected to the first inlets             of the first set of heat exchange bodies,         -   a second main distribution duct connected to the first             inlets of the second set of heat exchange bodies,     -   the first discharging means comprise a main discharging duct         connected to the first outlets of the first set and to the first         outlets of the second set of heat exchange bodies,     -   the first set of heat exchange bodies and the second set of heat         exchange bodies being arranged symmetrically with respect to the         main discharging duct.

According to one non-limiting embodiment, the heat exchange bodies are identical.

According to one non-limiting embodiment, the first set and the second set comprise the same number of heat exchange bodies so as to avoid any preferential passage of the fluid.

According to one non-limiting embodiment, for a heat exchange body of the first set and a heat exchange body of the second set, which are symmetric, the first inlet and the first outlet of each heat exchange body are provided in opposite walls of said heat exchange body, in a manner facing one another, in a median plane of said heat exchange body, said median plane being perpendicular to the axis along which said at least one main distribution duct extends or to the axis along which said at least one main discharging duct extends.

Such an arrangement makes it possible to further homogenize the distribution of the fluids between the different heat exchange bodies since the fluids follow the same path, making it possible to avoid a preferential passage in one of the heat exchange bodies.

According to one non-limiting embodiment, for a heat exchange body of the first set and a heat exchange body of the second set, which are symmetric, the first inlet and the first outlet of each heat exchange body are provided in opposite walls of said heat exchange body, in a manner offset axially from one another and arranged at an identical distance on either side of a median plane of said heat exchange body, said median plane being perpendicular to the axis along which said at least one main distribution duct extends or to the axis along which said at least one main discharging duct extends.

This embodiment is particularly advantageous when the manufacture of the heat exchange bodies does not make it possible to position the first inlet and the first outlet in the median plane of the heat exchange bodies. Thus, by offsetting the first inlet and the first outlet such that they are arranged at an identical distance on either side of a median plane of the heat exchange body, the fluids follow the same path, making it possible to avoid a preferential passage in one of the heat exchange bodies.

According to one non-limiting embodiment, said at least one main distribution duct of the first distribution means and said at least one main discharging duct of the first discharging means are configured to ensure circulation of the first fluid and of the second fluid, respectively, in opposite directions.

Such a configuration makes it possible to ensure U-shaped circulation of the fluids in the heat exchanger, making it possible to create a constant differential pressure between the first inlet and the first outlet of each heat exchange body. This makes it possible to maintain a pressure/temperature equilibrium point, thereby ensuring an optimized exchange of heat.

According to one non-limiting embodiment, the first distribution means and the first discharging means are disposed in one and the same horizontal plane.

According to one non-limiting embodiment,

-   -   each heat exchange body comprises:         -   a second inlet configured to receive the first fluid, and         -   a second outlet configured to discharge the second fluid,             and it comprises:             -   second distribution means for the first fluid, which are                 connected to the second inlets of the heat exchange                 bodies, the second distribution means comprising at                 least one main distribution duct,             -   second discharging means for the second fluid, which are                 connected to the second outlets of the heat exchange                 bodies, the second discharging means comprising at least                 one main discharging duct.

According to one non-limiting embodiment, the second distribution means and the second discharging means are disposed in one and the same vertical plane.

According to one non-limiting embodiment, said at least one main distribution duct of the second distribution means and the main discharging duct of the second discharging means are configured to ensure circulation of the first fluid and of the second fluid, respectively, in opposite directions.

Such a configuration makes it possible to ensure U-shaped circulation of the fluids in the heat exchanger, making it possible to create a constant differential pressure between the second inlet and the second outlet of each heat exchange body. This makes it possible to maintain a pressure/temperature equilibrium point, thereby ensuring an optimized exchange of heat.

A second aspect of the invention relates to a liquefaction system for liquefying a stream of gas with a dual refrigeration cycle, comprising:

-   -   a pre-cooling heat exchanger,     -   a liquefaction heat exchanger connected to the pre-cooling heat         exchanger,         the pre-cooling heat exchanger and/or the liquefaction heat         exchanger being a heat exchanger according to the first aspect         of the invention.

Aside from the features that have just been set out in the previous paragraph, the liquefaction system according to the second aspect of the invention may have one or more additional features from among the following, considered individually or in any technically possible combinations.

According to one non-limiting embodiment, a mixture manifold is arranged between the pre-cooling heat exchanger and the liquefaction heat exchanger, the mixture manifold being configured to mix an intermediate fluid exiting the pre-cooling heat exchanger before introducing it into the liquefaction heat exchanger.

The invention and the various applications thereof will be understood better from reading the following description and from studying the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

FIG. 1 shows a general schematic diagram of a liquefaction system with a dual refrigeration cycle according to the prior art.

FIG. 2 is a diagram illustrating a top view of a heat exchanger according to a first embodiment of the invention.

FIG. 3 is a diagram illustrating a top view of a heat exchanger according to a second embodiment of the invention.

FIG. 4 is a diagram illustrating a top view of a heat exchanger according to a third embodiment of the invention.

FIG. 5 is a diagram illustrating a top view of a heat exchanger according to a fourth embodiment of the invention.

FIG. 6 is a diagram illustrating a side view of a heat exchanger according to a fifth embodiment of the invention.

FIG. 7 is a diagram illustrating a side view of a liquefaction system with a dual refrigeration cycle according to one embodiment of the invention,

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The figures are given by way of indication and do not in any way limit the invention.

Unless specified to the contrary, the same element appearing in different figures has the same unique reference.

The invention relates to a heat exchanger particularly suitable for the liquefaction of a gas mixture, for example natural gas.

FIG. 2 illustrates a top view of a heat exchanger 100 according to a first embodiment of the invention.

With reference to FIG. 2, the heat exchanger 100 comprises:

-   -   heat exchange bodies 110,     -   distribution means 10,     -   discharging means 20.

The heat exchange bodies 110, in this case six heat exchange bodies 110, ensure the transfer of heat energy from a heat transfer fluid to a first fluid F1. Advantageously, the heat exchange bodies 110 are made of aluminium with brazed plates and fins. The heat exchange bodies 110 are identical and are distributed in two sets of heat exchange bodies 110: a first set S1 of heat exchange bodies 110 mounted in parallel and a second set 52 of heat exchange bodies 110 mounted in parallel. The first set S1 of heat exchange bodies 110 and the second set S2 of heat exchange bodies 110 comprise the same number of heat exchange bodies 110, in this case three heat exchange bodies 110 each. Furthermore, each heat exchange body 110 has a first inlet 111, through which the first fluid F1 is introduced, and a first outlet 112, through which a second fluid F2, obtained after the first fluid F1 has passed through the heat exchange body 110, is discharged.

The first set S1 and the second set S2 of heat exchange bodies 110 are supplied with first fluid F1 by the first distribution means 10. To this end, the first distribution means 10 comprise a main distribution duct 11, which extends longitudinally along an axis X1, arranged between the first set S1 and the second set S2 of heat exchange bodies 110. In particular, the heat exchange bodies 110 are arranged symmetrically with respect to the axis X1 of the main distribution duct 11. In other words, each heat exchange body 110 of the first set S1 is disposed in a manner facing a heat exchange body 110 of the second set S2 of heat exchange bodies 110.

The first distribution means 10 also comprise distribution channels 12 connected to the main distribution duct 11 and to the first inlets 111 of the first set S1 and the second set 52 of heat exchange bodies 110. Thus, the distribution means 10 comprise six distribution channels 12, one distribution channel 12 per heat exchange body 110, which extend perpendicularly to the axis X1 of the main distribution duct 11.

Furthermore, the second fluid F2 is discharged from the first set S1 and the second set S2 of heat exchange bodies 210 by the first discharging means 20. To this end, the first discharging means 20 comprise a first main discharging duct 21 and a second main discharging duct 23, which extend, respectively, along an axis X2 and along an axis X2′, which are parallel to the axis X1 of the main distribution duct 11. In particular, the axis X2 of the first main discharging duct 21 and the axis X2′ of the second main discharging duct 23 are arranged symmetrically with respect to the axis X1 of the main distribution duct 11.

The first discharging means 20 also comprise first discharging channels 22 connected to the first main discharging duct 21 and to the first outlets 112 of the first set S1 of heat exchange bodies 110. The first discharging channels 22 extend perpendicularly to the axis X2 of the first main discharging duct 21. Moreover, the discharging means 20 comprise second discharging channels 24 connected to the second main discharging duct 23 and to the first outlets 112 of the second set S2 of heat exchange bodies 110. The first discharging channels 22 extend perpendicularly to the axis X2′ of the second main discharging duct 23. Thus, the discharging means 20 comprise six discharging channels 22, 24, one discharging channel 22, 24 per heat exchange body 210.

Advantageously, the first distribution means 10 and the first discharging means 20 are disposed in one and the same horizontal plane. Furthermore, the main distribution duct 11 is configured to ensure circulation of the first fluid F1 in an opposite direction to the direction of circulation of the second fluid F2 in the first main discharging duct 21 and in the second main discharging duct 23. Thus, the first distribution means 10 and the first discharging means 20 ensure U-shaped circulation of the fluids F1, F2 in the heat exchanger 100.

Furthermore, the heat exchange bodies 110 have an overall shape substantially in the form of a rectangular parallelepiped. As can be seen in FIG. 2, the first inlet 111 and the first outlet 112 of each heat exchange body 110 are provided in opposite walls of the heat exchange body 110, in a manner facing one another. In particular, the first inlet 111 and the first outlet 112 of each heat exchange body 110 are disposed in one and the same median plane Pi of the heat exchange body 110 perpendicular to the axis X1 of the main distribution duct and to the axes X2, X2′ of the first and second main discharging ducts 21, 23.

FIG. 3 illustrates a top view of a heat exchanger 200 according to a second embodiment of the invention.

With reference to FIG. 3, the heat exchanger 200 according to the second embodiment comprises:

-   -   heat exchange bodies 210,     -   distribution means 30,     -   discharging means 40.

In the same way as in the first embodiment, the heat exchanger 200 comprises six heat exchange bodies 210. Advantageously, the heat exchange bodies 210 are made of aluminium with brazed plates and fins. The heat exchange bodies 210 are identical and are distributed in two sets of heat exchange bodies 210: a first set S1 of heat exchange bodies 210 mounted in parallel and a second set S2 of heat exchange bodies 210 mounted in parallel. The first set S1 of heat exchange bodies 210 and the second set S2 of heat exchange bodies 210 comprise the same number of heat exchange bodies 210, in this case three heat exchange bodies 210 each. Furthermore, each heat exchange body 210 has a first inlet 211, through which the first fluid F1 is introduced, and a first outlet 212, through which a second fluid F2, obtained after the first fluid F1 has passed through the heat exchange body 210, is discharged.

The first set S1 and the second set S2 of heat exchange bodies 210 are supplied with first fluid F1 by the first distribution means 30. To this end, the first distribution means 30 comprise a first main distribution duct 31 and a second main distribution duct 33, which extend, respectively, along an axis X3 and an axis X3′.

The first distribution means 30 also comprise first distribution channels 32 connected to the first main distribution duct 31 and to the first outlets 212 of the first set S1 of heat exchange bodies 210. The first distribution channels 32 extend perpendicularly to the axis X3 of the first main distribution duct 31. Moreover, the distribution means 30 comprise second distribution channels 34 connected to the second main distribution duct 33 and to the first outlets 212 of the second set S2 of heat exchange bodies 210. The second distribution channels 34 extend perpendicularly to the axis X3′ of the second main distribution duct 33. Thus, the distribution means 30 comprise six distribution channels 32, 34, one distribution channel 32, 34 per heat exchange body 310.

Furthermore, the second fluid F2 is discharged from the first set S1 and the second set S2 of heat exchange bodies 210 by the first discharging means 40. To this end, the first discharging means 40 comprise a main discharging duct 41, which extends longitudinally along an axis X4, arranged between the first set S1 and the second set S2 of heat exchange bodies 210. In particular, the heat exchange bodies 210 are arranged symmetrically with respect to the axis X4 of the main discharging duct 41. In other words, each heat exchange body 210 of the first set S1 is disposed in a manner facing a heat exchange body 210 of the second set S2 of heat exchange bodies 210. Moreover, the axis X4 of the main discharging duct 41 is parallel to the axes X3 and X3′, respectively, of the first main distribution duct 31 and of the second main distribution duct 33. In addition, the axis X3 of the first main distribution duct 31 and the axis X3′ of the second main distribution duct 33 are arranged symmetrically with respect to the axis X4 of the main discharging duct 41.

Moreover, the first discharging means 40 comprise discharging channels 42 connected to the main discharging duct 41 and to the first outlets 212 of the first set S1 and of the second set S2 of heat exchange bodies 210. Thus, the first discharging means 40 comprise six discharging channels 42, one discharging channel 42 per heat exchange body 210, which extend perpendicularly to the axis X4 of the main discharging duct 41.

Advantageously, the first distribution means 30 and the first discharging means 40 are disposed in one and the same horizontal plane. Furthermore, the first main distribution duct 31 and the second main distribution duct 33 are configured to ensure circulation of the first fluid F1 in an opposite direction to the direction of circulation of the second fluid F2 in the main discharging duct 41. In other words, the first distribution means 30 and the first discharging means 40 ensure U-shaped circulation of the fluids F1, F2 in the heat exchanger 200.

Furthermore, the heat exchange bodies 210 have an overall shape substantially in the form of a rectangular parallelepiped. As can be seen in FIG. 3, the first inlet 211 and the first outlet 212 of each heat exchange body 210 are provided in opposite walls of the heat exchange body 210, in a manner facing one another. In particular, the first inlet 211 and the first outlet 212 of each heat exchange body 210 are disposed in one and the same median plane P₁ of the heat exchange body 210. The median plane P₁ is perpendicular to the axes X3, X3′ of the first and second main distribution ducts 31, 33 and to the axis X4 of the main discharging duct 41.

FIG. 4 illustrates a top view of a heat exchanger 300 according to a third embodiment of the invention.

With reference to FIG. 4, the heat exchanger 400 according to the third embodiment comprises:

-   -   heat exchange bodies 310,     -   distribution means 50,     -   discharging means 60.

The heat exchanger 300 according to the third embodiment has the same features as the heat exchanger 100 according to the first embodiment, except that the first inlet 311 and the first outlet 312 of each heat exchange body 310 are offset axially from one another. In particular, the first inlet 311 and the first outlet 312 of each heat exchange body 310 are arranged at an identical distance on either side of a median plane P₁ of the heat exchange body 310. The median plane P₁ is perpendicular to the axis X5 along which the main distribution duct 51 extends and to the axes X6, X6′ along which the first main discharging duct 61 and the second main discharging duct 63, respectively, extend.

FIG. 5 illustrates a top view of a heat exchanger 400 according to a fourth embodiment of the invention.

With reference to FIG. 5, the heat exchanger 400 according to the fourth embodiment comprises:

-   -   heat exchange bodies 410,     -   distribution means 70,     -   discharging means 80.

The heat exchanger 400 according to the fourth embodiment has the same features as the heat exchanger 200 according to the second embodiment, except that the first inlet 411 and the first outlet 412 of each heat exchange body 410 are offset axially from one another. In particular, the first inlet 411 and the first outlet 412 of each heat exchange body 410 are arranged at an identical distance on either side of a median plane P₁ of the heat exchange body 410. The median plane P₁ is perpendicular to the axes X7, X7′ along which the first main distribution duct 71 and the second main distribution duct 73, respectively, extend and to the axis X8 along which the main discharging duct 81 extends.

FIG. 6 illustrates a side view of a heat exchanger 500 according to a fifth embodiment of the invention.

The heat exchanger 500 according to the fifth embodiment has the features of one of the above-described heat exchangers 100, 200, 300, 400. In addition to these features, the heat exchange bodies 510 comprise a second inlet 511 and a second outlet 512 that are configured to receive the first fluid F1 and discharge the second fluid F2, respectively.

To this end, the heat exchanger 500 comprises second distribution means 90 for the first fluid F1. In particular, the second distribution means 90 comprise a first main distribution duct 91 for supplying the first set S1 of heat exchange bodies 510 and a second main distribution duct (not illustrated) for supplying the second set S2 of heat exchange bodies 510 (not illustrated). The first main distribution duct 91 extends longitudinally along an axis X9. Advantageously, the second main distribution duct extends longitudinally along an axis parallel to the axis X9 of the first main distribution duct 91.

Moreover, the second distribution means 90 comprise first distribution channels 92 connected to the first main distribution duct 91 and to the second inlets 511 of the first set S1 of heat exchange bodies 510, The first distribution channels 90 extend perpendicularly with respect to the axis X9 along which the first main distribution duct 91 extends, In addition, the second distribution means 90 comprise second distribution channels (not illustrated) connected to the second main distribution duct and to the second inlets 511 of the second set S2 of heat exchange bodies 510. The second distribution channels extend perpendicularly with respect to the axis along which the second main distribution duct extends.

Furthermore, the heat exchanger 500 comprises second discharging means 95 for the second fluid F2. The second discharging means 95 comprise a first main discharging duct 96 for discharging the second fluid F2 from the first set S1 of heat exchange bodies 510 and a second main discharging duct (not illustrated) for discharging the second fluid F2 from the second set F2 of heat exchange bodies 510. The first main discharging duct 96 extends longitudinally along an axis X10. Advantageously, the second main discharging duct extends longitudinally along an axis parallel to the axis X10 of the first main discharging duct 96.

Moreover, the second discharging means 95 comprise first discharging channels 97 connected to the first main discharging duct 96 and to the second outlets 512 of the first set S1 of heat exchange bodies 510. The first discharging channels 97 extend perpendicularly with respect to the axis X10 along which the first main discharging duct 96 extends. In addition, the second discharging means 95 comprise second discharging channels (not illustrated) connected to the second main discharging duct and to the second outlets 512 of the second set S2 of heat exchange bodies 510. The second discharging channels extend perpendicularly with respect to the axis along which the second main discharging duct extends,

Advantageously, the second distribution means 90 and the second discharging means 95 are disposed in one and the same vertical plane, Furthermore, the first main distribution duct 91 of the second distribution means 90 is configured to ensure circulation of the first fluid F1 in an opposite direction to the direction of circulation of the second fluid F2 in the first main discharging duct 96 of the second discharging means 95, In the same way, the second main distribution duct of the second distribution means 90 is configured to ensure circulation of the first fluid F1 in an opposite direction to the direction of circulation of the second fluid F2 in the second main discharging duct of the second discharging means 95. In other words, the second distribution means 90 and the second discharging means 95 ensure U-shaped circulation of the fluids F1, F2 in the heat exchanger 500,

Furthermore, as can be seen in FIG. 6, the second inlet 511 and the second outlet 512 of each heat exchange body 510 are provided in opposite walls of the heat exchange body 510, in a manner facing one another. In particular, the second inlet 511 and the second outlet 512 of each heat exchange body 510 are disposed in one and the same median plane P₂ of the heat exchange body 510. The median plane P₂ is perpendicular to the axes X9, X10, respectively, of the main distribution ducts 91 and of the main discharging ducts 96,

In an embodiment variant that is not illustrated, the second inlet 511 and the second outlet 512 of each heat exchange body 510 are provided in opposite walls of the heat exchange body 510, in a manner axially offset from one another. In particular, the second inlet 511 and the second outlet 512 of each heat exchange body 510 are arranged at an identical distance on either side of a median plane P₂ of the heat exchange body 510, The median plane P₂ is perpendicular to the axes X9, X10, respectively, of the main distribution ducts 91 and of the main discharging ducts 96. Advantageously, the second inlet 511 and the second outlet 512 of all of the heat exchange bodies 510 are arranged at an identical distance from the median plane P₂.

Furthermore, the invention also relates to a liquefaction system 600 with a dual refrigeration cycle comprising at least one of the above-described heat exchangers 100, 200, 300, 400, 500.

FIG. 7 illustrates a liquefaction system 600 according to one embodiment of the invention.

With reference to FIG. 7, the liquefaction system 600 comprises:

-   -   a pre-cooling heat exchanger 610,     -   a liquefaction heat exchanger 620.

The pre-cooling heat exchanger 610 is supplied with a first fluid F1′, for example natural gas. Advantageously, the pre-cooling heat exchanger 610 is formed by one of the above-described heat exchangers 100, 200, 300, 400, 500.

A mixture manifold 650 is positioned at the outlet of the pre-cooling heat exchanger 610 in order to mix an intermediate fluid F1″ obtained after the first fluid F1′ has passed through the pre-cooling heat exchanger 610. Specifically, the intermediate fluid F1″ collected is formed by a mixture of fluids coming from several heat exchange bodies, in particular from one or more outlets of one and the same heat exchange body.

After it has been mixed, the intermediate fluid F1″ is then introduced into the liquefaction heat exchanger 620. Advantageously, the liquefaction heat exchanger 620 is formed by one of the above-described heat exchangers 100, 200, 300, 400, 500.

A second fluid F1″40 , obtained after the intermediate fluid F1″ has passed through the liquefaction heat exchanger 620, is then discharged towards storage tanks.

It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above. 

What is claimed is:
 1. A heat exchanger comprising: a plurality of heat exchange bodies, each heat exchange body comprising: a first inlet configured to receive a first fluid, a first outlet configured to discharge a second fluid, a first distribution means for the first fluid, which is connected to the first inlets of the heat exchange bodies, the first distribution means comprising at least one main distribution duct, a first discharging means for the second fluid, which is connected to the first outlets of the heat exchange bodies, the first discharging means comprising at least one main discharging duct, wherein the plurality of heat exchange bodies comprise a first set of heat exchange bodies mounted in parallel and a second set of heat exchange bodies mounted in parallel, and the first set of heat exchange bodies and the second set of heat exchange bodies being disposed symmetrically with respect to said at least one main distribution duct of the first distribution means or with respect to said at least one main discharging duct of the first discharging means.
 2. The heat exchanger according to the claim 1, wherein: the first distribution means comprises a main distribution duct connected to the first inlets of the first set and to the first inlets of the second set of heat exchange bodies, the first discharging means comprises: a first main discharging duct connected to the first outlets of the first set of heat exchange bodies, a second main discharging duct connected to the first outlets of the second set of heat exchange bodies, the first set of heat exchange bodies and the second set of heat exchange bodies being arranged symmetrically with respect to the main distribution duct.
 3. The heat exchanger according to claim 1, wherein: the distribution means comprises: a first main distribution duct connected to the first inlets of he first set of heat exchange bodies, a second main distribution duct connected to the first inlets of the second set of heat exchange bodies, the first discharging means comprises a main discharging duct connected to the first outlets of the first set and to the first outlets of the second set of heat exchange bodies, the first set of heat exchange bodies and the second set of heat exchange bodies being arranged symmetrically with respect to the main discharging duct.
 4. The heat exchanger according to claim 1, wherein the heat exchange bodies are identical.
 5. The heat exchanger according to claim 1, wherein the first set and the second set comprise the same number of heat exchange bodies.
 6. The heat exchanger according to claim 1, wherein, for a heat exchange body of the first set and a heat exchange body of the second set, which are symmetric, the first inlet and the first outlet of each heat exchange body are provided in opposite walls of said heat exchange body, in a manner facing one another, in a median plane of said heat exchange body, said median plane being perpendicular to the axis along which said at least one main distribution duct extends or to the axis along which said at least one main discharging duct extends.
 7. The heat exchanger according to claim 1, wherein, for a heat exchange body of the first set and a heat exchange body of the second set, which are symmetric, the first inlet and the first outlet each heat exchange body are provided in opposite walls of said heat exchange body, in a manner offset axially from one another and arranged at an identical distance on either side of a median plane of said heat exchange body, said median plane being perpendicular to the axis along which said at least one main distribution duct extends or to the axis along which said at least one main discharging duct extends.
 8. The heat exchanger according to claim 1, wherein the at least one main distribution duct of the first distribution means and said at least one main discharging duct of the first discharging means are configured to ensure circulation of the first fluid and of the second fluid, respectively, in opposite directions.
 9. The heat exchanger according to claim 1, wherein the first distribution means and the first discharging means are disposed in one and the same horizontal plane.
 10. The heat exchanger according to claim 1, wherein: each heat exchange body comprises: a second inlet configured to receive the first fluid, and a second outlet configured to discharge the second fluid, and further comprising: a second distribution means for the first fluid, which are connected to the second inlets of the heat exchange bodies, the second distribution means comprising at least one main distribution duct, a second discharging means for the second fluid, which are connected to the second outlets of the heat exchange bodies, the second discharging means comprising at least one main discharging duct.
 11. The heat exchanger according to the claim 10, wherein the second distribution means and the second discharging means are disposed in one and the same vertical plane.
 12. The heat exchanger according to claim 10, wherein the at least one main distribution duct of the second distribution means and the main discharging duct of the second discharging means are configured to ensure circulation of the first fluid and of the second fluid, respectively, in opposite directions.
 13. A liquefaction system for liquefying a stream of gas with a dual refrigeration cycle, comprising: a pre-cooling heat exchanger, a liquefaction heat exchanger connected to the pre-cooling heat exchanger, wherein the pre-cooling heat exchanger and/or the liquefaction heat exchanger is/are a heat exchanger according to claim
 1. 14. The liquefaction system according to claim 13, wherein a mixture manifold is arranged between the pre-cooling heat exchanger and the liquefaction heat exchanger, the mixture manifold being configured to mix an intermediate fluid exiting the pre-cooling heat exchanger before introducing it into the liquefaction heat exchanger. 